*Remove 'first_spell' and 'rank' columns from table spell_chain

*Separate req_spell and spell_chain data to save some memory
*Use spell_chain data generated from dbc instead of sql

--HG--
branch : trunk

sql/updates/571_world.sql

@@ -0,0 +1,5 @@
+ALTER TABLE spell_chain DROP COLUMN first_spell;
+ALTER TABLE spell_chain DROP COLUMN rank;
+ALTER TABLE spell_chain RENAME TO spell_required;
+DELETE FROM spell_required WHERE req_spell=0;
+